Tennis ball

ABSTRACT

A tennis ball may include a spherical hollow elastomeric core having a specific gravity of less than 1 and a thickness of at least 4.5 mm and a textile layer covering the spherical hollow core

BACKGROUND

Tennis balls are typically pressurized to enhance rebound or bounceperformance. As a pressure in the ball decreases, the tennis balls loserebound or bounce performance. This loss is accelerated by play. As aresult, the tennis balls must often be replaced. Prior to initial use,such tennis balls must be packaged in pressurized containers to maintaintheir performance characteristics prior to such initial use.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an example tennis ball.

FIG. 2 is a sectional view of the tennis ball of FIG. 1 taken along line2-2.

FIG. 3 is an exploded side view of the tennis ball of FIG. 1.

FIG. 4 is a sectional view of an example tennis ball package having aset of the tennis balls of FIG. 1 packaged in a package.

Throughout the drawings, identical reference numbers designate similar,but not necessarily identical, elements. The figures are not necessarilyto scale, and the size of some parts may be exaggerated to more clearlyillustrate the example shown. Moreover, the drawings provide examplesand/or implementations consistent with the description; however, thedescription is not limited to the examples and/or implementationsprovided in the drawings.

DETAILED DESCRIPTION OF EXAMPLES

Disclosed herein are examples of tennis balls that maintain performanceover longer periods of time and play, increasing the longevity of thetennis ball. The increased playable life of such tennis balls reduceswaste, and reduces the frequency in which players, club and/ororganizations purchase replacement tennis balls. Disclosed herein areexample low-pressure tennis balls that have performance characteristicssimilar to higher pressurized tennis balls, facilitating the packagingof such tennis balls in lower pressure or pressure-less packages.Disclosed herein are example tennis balls that exhibit the performanceof a premium tennis ball and maintain that high level of performanceover prolonged periods of time.

Disclosed herein are example tennis balls having characteristics thatsatisfy standards and regulations pertaining to tennis balls utilized incompetitive play as established by the United States Tennis Associationand International Tennis Federation while, at the same time, providingsuch enhanced performance longevity. For purposes of this disclosure, a“competitive play tennis ball” means a tennis ball that satisfies thefollowing specifications as currently published by the InternationalTennis Federation and set forth below.

-   -   a. The ball shall have a uniform outer surface consisting of a        fabric cover except for the Stage 3 (Red) foam ball. If there        are any seams they shall be stitchless.    -   b. The ball shall conform to one of types specified in the table        immediately below or in the table under paragraph (d).

Type 1 Type 2 Type 3 — (Fast) (Medium)¹ (Slow)² High Altitude³ Mass56.0-59.4 g 56.0-59.4 g 56.0-59.4 g 56.0-59.4 g (Weight) (1.975-2.095oz) (1.975-2.095 oz) (1.975-2.095 oz) (1.975-2.095 oz) Size 6.54-6.86 cm6.54-6.86 cm 7.00-7.30 cm 6.54-6.86 cm (2.57-2.70 in) (2.57-2.70 in)(2.76-2.87 in) (2.57-2.70 in) Rebound 138-151 cm 135-147 cm 135-147 cm122-135 cm (54-60 in) (53-58 in) (53-58 in) (48-53 in) Forward 0.56-0.74cm 0.56-0.74 cm 0.56-0.74 cm 0.56-0.74 cm Deformation⁴ (0.220-0.291 in)(0.220-0.291 in) (0.220-0.291 in) (0.220-0.291 in) Return 0.74-1.08 cm0.80-1.08 cm 0.80-1.08 cm 0.80-1.08 cm Deformation⁴ (0.291-0.425 in)(0.315-0.425 in) (0.315-0.425 in) (0.315-0.425 in) Colour White or Whiteor White or White or Yellow Yellow Yellow Yellow Notes: ¹This ball typemay be pressurised or pressureless. The pressureless ball shall have aninternal pressure that is no greater than 7 kPa (1 psi) and may be usedfor high altitude play above 1,219 m (4,000 feet) above sea level andshall have been acclimatised for 60 days or more at the altitude of thespecific tournament. ²This ball type is also recommended for highaltitude play on any court surface type above 1,219 m (4,000 feet) abovesea level. ³This ball type is pressurised and is an additional ballspecified for high altitude play above 1,219 m (4,000 feet) above sealevel only. ⁴The deformation shall be the average of a single readingalong each of three perpendicular axes. No two individual readings shalldiffer by more than 0.08 cm (0.031 inches).

-   -   c. In addition, all ball types specified under paragraph (b)        shall conform to the requirements for durability as shown in the        following table:

Mass Forward Return — (Weight) Rebound Deformation Deformation Maximum0.4 g 4.0 cm 0.08 cm 0.10 cm Change¹ (0.014 oz) (1.6 in) (0.031 in)(0.039 in) Notes: ¹The largest permissible change in the specifiedproperties resulting from the durability test described in the currentedition of ITF Approved Tennis Balls, Classified Surfaces & RecognisedCourts. The durability test uses laboratory equipment to simulate theeffects of nine games of play.

-   -   d. Only the ball types specified in the table below can be used        in 10 and under tennis competition:

Stage 3 Stage 3 Stage 2 Stage 1 (Red) (Red) (Orange) (Green) — FoamStandard Standard Standard Mass 25.0-43.0 g 36.0-49.0 g 36.0-46.9 g47.0-51.5 g (Weight) (0.882-1.517 oz) (1.270-1.728 oz) (1.270-1.654 oz)(1.658-1.817 oz) Size 8.00-9.00 cm 7.00-8.00 cm 6.00-6.86 cm 6.30-6.86cm (3.15-3.54 in) (2.76-3.15 in) (2.36-2.70 in) (2.48-2.70 in) Rebound85-105 cm 90-105 cm 105-120 cm 120-135 cm (33-41 in) (35-41 in) (41-47in) (47-53 in) Forward — — 1.40-1.65 cm 0.80-1.05 cm Deformation¹(0.551-0.650 in) (0.315-0.413 in) Colour² Any Red and Orange and Yellowwith a Yellow, Yellow, Green dot or Yellow or Yellow with with a an Reddot Orange dot Notes: ¹The deformation shall be the average of a singlereading along each of three perpendicular axes. There is no limit on thedifference between individual forward deformation readings. There is nospecification for return deformation. ²All coloured dots shall bereasonable in size and placement.

-   -   e. All tests for rebound, mass, size, deformation and durability        shall be made in accordance with the Regulations described in        the current edition of ITF Approved Tennis Balls, Classified        Surfaces & Recognised Courts.

Disclosed herein are example tennis balls that are more environmentallyfriendly. The disclosed tennis balls last significantly longer, reducingwaste. The longer useful life of the example tennis balls allows forplayers to use the balls for a longer period of time, thereby discardingfully used balls and obtaining replacement balls less frequently thanconventional tennis balls. The disclosed tennis balls maintainperformance at or near atmospheric pressure such that the tennis ballsmay be packaged in low pressure or non-pressurized packages, as aresult, the example tennis balls may be packaged in more environmentallyfriendly packaging.

The disclosed tennis balls are further ideal for tennis clubs or otherlocations where a large number of tennis balls are often placed intobins or baskets for lessons and/or practice. As a result, differentballs may have different performance characteristics depending upontheir age and wear, providing inconsistent performance. Suchinconsistency amongst the balls may make lessons and practice lessproductive and less enjoyable. The different ages of the differenttennis balls in such baskets may further present a challenge for clubsor resorts to maintain baskets and bins with playable balls. Thedisclosed tennis balls have performance longevity such that they do notexperience substantial performance degradations over time. Because thedisclosed tennis balls will have a useful playable life of six months ormore, the large number of tennis balls contained in such baskets orpackages may have more consistent and uniform performancecharacteristics.

Disclosed herein are example tennis balls that may include a sphericalhollow elastomeric core having a specific gravity of less than 1.0 and athickness of at least 4.5 mm and a textile layer covering the sphericalhollow core. For purposes of this disclosure, “specific gravity” is aratio of the density of the substance to the density of a referencesubstance, namely, water, at room temperature and atmospheric pressure.

Disclosed herein are example tennis balls that comprise a sphericalhollow elastomeric core and a textile layer covering the sphericalhollow core. The tennis balls are competitive play tennis balls in thatthe tennis balls have characteristics that satisfy United States TennisAssociation and International Tennis Federation standardizedspecifications as published by the International Tennis Federation as ofJul. 1, 2018. The competitive play tennis balls exhibit a reboundpercentage decline of less than 4% after four months of nonuse andexposure to atmospheric pressure. In other implementations, thecompetitive play tennis balls exhibit a rebound percentage decline ofless than 3% after four months of nonuse and exposure to atmosphericpressure.

Disclosed herein are example tennis ball packages that comprise apackage at a pressure of no greater than 5 psi and a set of tennis ballswithin the package. Each of the tennis balls exhibits a reboundpercentage decline of less than 4% after four months of nonuse andexposure to atmospheric pressure upon removal from the sealed package.In other implementations, the competitive play tennis balls exhibit arebound percentage decline of less than 3% after four months of nonuseand exposure to atmospheric temperature.

Disclosed herein are example tennis ball packages that comprise apackage at a pressure of no greater than 10 psi and a plurality oftennis balls within the package. At least one of the plurality of tennisballs has a first tennis ball coefficient of restitution value of atleast 0.53 when measured from an initial velocity of 90 feet/secondwithin 1 hour of the at least one of the plurality of tennis balls beinginitially removed from the tennis ball package and unused, and a secondtennis ball coefficient of restitution value measured from an initialvelocity of 90 feet/second after the at least one of the plurality oftennis balls is exposed to atmospheric pressure for four months. Thesecond coefficient of restitution value is at least 95 percent of thefirst coefficient of restitution value.

FIGS. 1-3 illustrate an example tennis ball 10. FIG. 1 is a perspectiveview of tennis ball 10. FIG. 2 is a sectional view of tennis ball 10taken along line 2-2 of FIG. 1. FIG. 3 is an exploded view of tennisball 10 Tennis ball 10 maintains performance over longer periods of timeand play, increasing the longevity of the tennis ball 10. Tennis ball 10has performance characteristics similar to higher pressurized tennisballs, facilitating the packaging of tennis ball 10 in lower pressurepackages. Tennis ball 10 may be manufactured in warmer environments orpackaged in warmer environments with less risk of a negative or vacuumpressure occurring within the tennis ball 10 when at room temperature orat lower temperatures. Tennis ball 10 may be packaged in lesspressurized or in unpressurized packages while maintaining performanceover prolonged periods of time.

As shown by FIGS. 1 and 2, tennis ball 10 comprises outer textile layer12 and core 14. Outer textile layer 12 comprises at least one layer offabric material secured over and about core 14. As shown by FIGS. 1 and3, in one implementation, outer textile layer 12 comprises twointer-nested “stadium-shaped” shaped panels 16 of textile materialbonded to core 14 (as shown in FIGS. 2 and 3) along seams 18. In otherimplementations, outer textile layer 12 may be provided by panels havingother shapes, such as, for example, dog bone-shaped. In someimplementations, textile layer 12 may be formed by fibers not providedin the form of panels, but which are individually or collectively joinedor bonded to core 14.

In one implementation, tennis ball 10 may be formed by bathing orcoating the core 14 in an adhesive, such as a synthetic or naturalrubber adhesive. In such an implementation, the outer edges of at leastone of the two dog-bone or stadium shaped panels 16 of textile materialare coated with an adhesive, such as a synthetic or natural rubberadhesive. The dog-bone shaped panels 16 are then applied over and to thecore 14 with the edges of the dog-bone shaped panels 16 in abutment orclose proximity along a seam comprised of the bonding adhesive, whilethe adhesives are in an adhesive state to form the tennis ball shown inFIG. 1. The adhesive is then allowed to dry or cure.

In one implementation, outer textile layer 12 comprises a layer of fibermaterial such as felt. In one implementation, outer textile layer 12comprise a woven fiber material. In one implementation, outer textilelayer 12 comprises a needle-punched fiber material. In yet otherimplementations, outer textile layer 12 may comprise other materials.

In one such implementation, the outer textile layer comprises a layer offelt adhered core 14 using a rubber-based adhesive. The felt applied tothe cover may comprise woven fiber material or needle punched felt. Feltmay comprise natural fiber (such as wool), synthetic fiber (such asnylon) or a mixture thereof. In one implementation, the felt cover maycomprise a needle-punched felt comprising fiber having a wool content of70% and a nylon content 30%. The needle punched felt may have a highlevel of elongation. For example, the felt can have a diagonal directionelongation of greater than 12% under an applied load of five psi. Inother implementations, other mixtures of natural and synthetic fiberscan be used. In other implementations, felts having other elongationvalues can be used.

Core 14 comprises a hollow spherical structure having a spherical wallformed from a rubber or rubber-like material. In one implementation,core 14 is formed from two semi-spherical halves or half shells 20-1,20-2 which are molded, joined and/or bonded together. In oneimplementation, an adhesive 22, such as a natural rubber or syntheticrubber adhesive, can be used to join or bond the half shells 20-1 and20-2 together. In one implementation, the two semi spherical halves orhalf shells 20-1, 20-2 are joined in a pressure chamber so the interiorof the joined halves is pressurized. In one implementation, the twosemi-spherical halves or half shells 20-1, 20-2 are adjoined in apressure chamber such that the interior of the joined halves has apressure of no greater than five psi. In other implementations, theinternal pressure of the formed core can be approximately, four psi,three psi, two psi or 1 psi. In other implementations, core 14 may beformed in other manners. In some implementations, core 14 mayadditionally incorporate a valve that facilitates pressurization of theinterior of core 14. In other implementations, the core 14 may be formedin a non-pressurized chamber and pressurized during the molding orcuring process without the use of a valve attached to the core.

In the example illustrated, core 14 has a thickness T (shown in FIG. 2)of at least 4.8 mm. In one implementation, the thickness T of core 14 isat least 4.8 mm and no greater than 5.1 mm. In another implementation,the core can have a thickness T of at least 4.5 mm. The core thicknessof a conventional pressurized tennis ball core is approximately 3.5 mm.The core has a specific gravity of less than 1.0. In one implementation,the specific gravity is approximately 0.985. In other implementations,the formulation of the core can have a specific gravity of 0.99 or less.In other limitations, the core can have a density of less than or equalto 1.0 g/cm³.

In one implementation, core 14 comprises an ethylene copolymer having aspecific gravity of less than 0.9. In one implementation, the ethylenecopolymer has a specific gravity of less than 0.9, a flexural modulus ofless than 35 MPA and a shore D hardness of less than 30. In anotherimplementation, the flexural modulus of the ethylene copolymer can beless than or equal to 25 MPA. The core 14 can include one more ethylenecopolymers. The alkene of the one or more ethylene copolymers can be abutene, hexene, octene, pentene, heptene, nonene and decene.

In one implementation, the core comprises at least one rubber selectedfrom a group consisting of natural rubber, polybutadiene, polyisoprene,styrene-butadiene rubber and/or mixtures thereof. In someimplementations, the core may additionally comprise fillers, activators,accelerators, retardants and the like, a sulfur vulcanizing agent and/oran ethylene copolymer having a specific gravity of less than 0.9. In oneimplementation, the core 14 is formed from a blend of rubbers comprisingpolybutadiene rubber, natural rubber and styrene-butadiene rubber, and athermoplastic co-polymer comprising ethylene and butane, zinc oxide asan activator, silica as a filler for weight and a stiffening agent,accelerators, retarders, antioxidants and sulfur to vulcanize thepolymer composition.

In some implementations, the ethylene copolymer may comprise copolymersof ethylene with butane, hexane or octane, a blend thereof. Some examplematerials include, not limited to, the material sold under the tradename ENGAGE® and commercially available from The Dow Chemical Company ofMidland, Mich., or a material sold under the trade name EXACT® by ExxonMobil Corporation of Irving, Tex.

In one implementation, the ethylene copolymer is Dow® ENGAGE® 7270 whichis a copolymer of ethylene and butane having a specific gravity of0.880, a flexural modulus of 22.1 MPA and a durometer on the Shore Dhardness scale of 26. In one such implementation, the outer textilelayer comprises a layer of felt adhered to the core 14 using arubber-based adhesive.

One example tennis ball 10 (Example 1) comprises a core 14 comprisesDow® ENGAGE® 7270, a copolymer of ethylene and butane having a specificgravity of 0.880, a flexural modulus of 22.1 MPA and a Shore D hardnessor durometer value of 26. The core 14 has a thickness of 4.8 mm. Theexample tennis ball 10 (Example 1) has an outer textile layer 12comprising a needle-punched felt formed from a fiber having a woolcontent of 70% and a nylon continent 30%. The outer textile layer 12 isadhered to the surface of core 14 using a rubber-based adhesive.

Table 1 below illustrates comparison of various properties of the twoExample 1 tennis balls (PLB-5B) with that of a Wilson® US OPEN ExtraDuty tennis ball produced by Wilson Sporting Goods Co. of Chicago, Ill.The Wilson® US OPEN Extra Duty tennis ball is a top-line commerciallyavailable tennis ball configured for competitive play and similar to thetennis balls used at the U.S. Open major tennis tournament.

Tennis ball characteristics and performance data were measured andrecorded for sets of 6 tennis balls from each of the two exampleprototype tennis balls (PLB-5B) and the Wilson® U.S. Open tennis balls.The characteristics and performance data included internal ballpressure, ball size, ball weight, ball deformation, ball rebound height,and coefficient of restitution (COR) values taken from various inboundball speeds.

Internal ball pressure is measured by puncturing the surface of the ballwith a needle attached to a pressure gauge. Tennis ball deformation ismeasured using a Stevens Machine by Redland of Crawley, England, or aconventional automatic compression machine. A Stevens Machine formeasuring tennis ball deformation is a compression machine designed byPercy Herbert Stevens and patented under GB Patent No. 230250. Tennisball deformation is measured by placing the tennis ball into thecompression machine and applying a pre-load compressive force of 3.5 lbfto the ball and zeroing the deformation indicator of the compressionmachine, then applying an additional compressive load of 18.0 lbf andrecording the deformation of the ball with respect to the initialpre-load deformation value. Three deformation readings are taken on eachball with the ball rotated 90 degrees between each reading/measurement.

Tennis ball rebound height is measured from the bottom of a tennis ballbeing vertically dropped from a height of 100 inches off of a graniteplate having a smooth surface and a thickness of at least 1.25 inches.As stated above, tennis balls configured for competitive play typicallyhave rebound characteristics falling within the range of 53 to 58inches, and a range of 48 to 53 inches for play in high altitudeconditions. The term “tennis ball rebound height” shall mean ameasurement of the maximum height of the bottom of a tennis ballrecorded after the tennis ball is dropped from an initial height of 100inches above a granite plate having a smooth surface.

Tennis ball COR measurements are taken by projecting the ball at aninitial velocity (e.g. 60 fps, 90 fps or 120 fps) off of a rigidlymounted, vertically positioned steel plate having a smooth surface and athickness of 1 inch, and measuring the velocity of the ball reboundingfrom the steel plate using light gates, such as model ADC VG03 byAutomated Design Corporation of Romeoville, Ill. The tennis balls can beprojected using a pneumatic cannon, such as an ADC Air Cannon byAutomated Design Corporation of Romeoville, Ill., or other comparableball launching apparatus to obtain the initial ball speeds of 60 fps, 90fps or 120 fps. The term “tennis ball coefficient of restitution value”means a tennis ball COR measurement taken from a specified initialvelocity off of a vertically positioned, rigidly mounted steel platehaving a smooth surface and measuring the velocity of the ballrebounding from the steel plate using light gates.

TABLE 1 Request No.: B180131 Date: Jan. 31, 2018 Name: Cacloppo PLB-5BPLB-5B UNIS Smaller Tooling Smaller Tooling T1062 TARGET No ExpancelExpancel Foam US Open SPECS. Pressurized Pressurized Extra Duty(Pressurized) QTY Can Can Control COMMENTS CORE 6 PLB-5B PLB-5B U-005SCOMPOUND WALL 6 4.8 mm 4.8 mm 3.4 mm THICKNESS FELT 6 3602N 3602N 3336LOGO 6 US Open 1 US Open 3 US Open 4 CAN PRESS. Avg. 13.0-15.0 6 6.7 6.014.7 (psi) Stdev. 0.1 0.1 0.1 BALL PRESS. Avg. 12.0-14.0 6 4.5 3.7 13.8AFTER COR Stdev. 0.1 0.1 0.2 SIZE: Avg. 2.600-2.680 6 2.623 2.620 2.647High Rebound (in.) Stdev. 0.010 0.000 0.008 w/ Zero G USO 1 WEIGHT: Avg.56.0-59.5 6 57.0 57.5 58.1 (g) Stdev. 0.4 0.4 0.6 DEFORM.: Avg..230-.260 6 .228 .234 .233 (in.) Stdev. 005 004 .005 REBOUND: Avg.54.0-58.0 6 60.3 58.3 57.9 (in.) Stdev. 0.5 0.2 0.5 COR @ 60 fps Avg. 6.653 .648 .664 Stdev. 008 .010 .010 COR @90 fps Avg. 6 .543 .524 .559Stdev. .008 .008 .008 COR @ 120 fps Avg. 6 .463 .442 .486 Stdev. .006.007 .008 MOI (oz.-in 2) Avg. 6 1.776 1.761 1.931 Zero G was (Moment ofInertia) Stdev. .021 .014 .029 8.0% Lower in MOI than US Open ControlBall

As shown above, the two tested Example 1 tennis balls (PLB-5B) havesimilar performance characteristics as that of the pressurized Wilson®US OPEN tennis balls except for moment of inertia (MOI) of the tennisballs. The Example 1 tennis balls exhibit a MOI that is 8 percent lowerthan the Wilson® US OPEN tennis balls tested. This greater wallthickness of core 14 of the Example 1 tennis balls contributes to thereduced MOI values as compared to the wall thickness of the Wilson® USOPEN tennis balls. The lower MOI can facilitate the application of spinto the Example 1 tennis balls. The ability for a player to impart spinto a tennis ball during play is important for many tennis players,particularly highly skilled tennis players who often impart topspin tothe ball upon impact during play. Two groups of tennis balls underPLB-5B were prepared, one group incorporated Expancel foam during itsmanufacture and the other group was produced without the use of Expancelfoam. Expancel comprises microspheres that expand under heat to up to 40times their size. The microspheres can be placed inside core shellsprior to molding and then expand under heat to fill the volume withinthe molded core during the molding process. In some core compositions,Expancel can improve the sound characteristics of the ball. Expancelfoam is produced by AkzoNobel Chemical Products. Test results indicatethat the use of Expancel is not necessary when an ethylene-butenecopolymer such as Engage is incorporated into the core composition.

In one implementation, the tennis ball can have a moment of inertia ofless than 1.85 oz-in². In other implementations, the tennis ball canhave a moment of inertia of less than 1.80 oz-in². The tennis ballsbuilt in accordance with a present implementation of the presentinvention can have a lower MOI than conventional tennis balls andtherefore allow for a player to more easily impart spin to the ballduring use, thereby improving the player's control and/or the player'sability to hit the ball harder while keeping the ball in play.

Table 2 below is a summary of the properties of the example tennis ball10 (Example 1) with respect to a commercial Wilson® US OPEN tennis ball,a premium pressurized tennis ball having an internal pressure ofapproximate 13 psi.

TABLE 2 Physical Properties: C.O.R. 120 Ball Press. Size Wt. Def. Reb 60f/s 90 f/s f/s Example 1 3.7 2.623″ 57.0 0.234″ 58.6 0.653 0.543 0.463(ZERO G) Wilson ® 13.8 2.647″ 58.1 0.233″ 57.6 0.664 0.559 0.486 US Open

As shown above, the Example 1 tennis ball has an internal pressure of3.7 psi, significantly lower than the Wilson® US Open tennis ball, andother commercially available tennis balls used in competitive play. TheExample 1 tennis ball also has size, weight, deformation and reboundcharacteristics that are comparable to the WILSON® US OPEN tennis balland is a competitive tennis ball, within the requirements set forth bythe USTA and the ITF. Example 1 tennis ball also has coefficient ofrestitution properties that are comparable to a pressurized tennis ball,the WILSON® US OPEN tennis ball.

The Example 1 tennis ball has prolonged performance longevity ascompared to the WILSON® US OPEN tennis ball. Table 3 below providespermeation data for the Example 1 tennis balls and the WILSON® US OPENtennis balls at different times following removal of the tennis ballsfrom their respective pressurized packages or cans.

TABLE 3 OUT-of-CAN 1, 2, 3, 4, 5, and 6 months BALL PARAMETER QTY.Initial (1) mo. (2) mo. (3) mo. (4) mo. (5) mo. (6) mo. WRT1062 BALLPRESS.: (psi) 6 13.7 11.2 9.0  7.6 — — — US Open REBOUND: (in.) 6 56.355.3 54.5 52.8 — — — (Contol) WRT1062 BALL PRESS.: (psi) 6 13.4 — 8.8 — 6.5 — May 7, 2018 US Open REBOUND: (in.) 6 57.5 — 54.3 — 54.5 — May 7,2018 (Contol) ZERO G BALL PRESS.: (psi) 6 4.3  3.1 1.9  1.2 — — — PLB-5REBOUND: (in.) 6 59.7 60.3 60.0 59.6 — — — (4.1) mm ZERO G BALL PRESS.:(psi) 6 4.9 — 1.8 —  1.1 —  0.7 PLB-5B REBOUND: (in.) 6 58.8 — 57.7 —57.2 — 57.8 (4.8) mm

As demonstrated by Table 3 above and the graph and Table 4 below, thetennis balls made in accordance with an implementation of the presentapplication, maintain their rebound height over time. In particular, therebound height is at least 96% of the initial rebound height even after4 months of the balls being maintained in an atmospheric pressureenvironment. In another implementation, the rebound is height is atleast 97% of the initial rebound height after four months of beingmaintained in an atmospheric pressure environment. In oneimplementation, the height of the rebound of an Example prototype tennisball from the surface, has a first tennis ball rebound height that isrecorded by measuring the rebound of the tennis ball within 1 hour ofbeing initially removed from the tennis ball package and unused, and asecond tennis ball rebound height that is recorded by measuring therebound of the tennis ball after the tennis ball is exposed toatmospheric pressure for four months and unused, and the second reboundheight at least 96% of the first rebound height. In anotherimplementation, the second rebound height is at least 97% of the firstrebound height.

The graph below provides a comparison between the Example 1 and WILSON®US OPEN tennis balls which were tested for rebound within 1 hour afterbeing initially removed from pressurized cans and unused and thenre-measured after two-month intervals. In the example illustrated, theExample 1 tennis balls were initially pressurized at a pressure of nogreater than 7 psi (6.7 psi and 6.0 psi) whereas the WILSON® US OPENtennis balls were contained in cans were initially pressurized at apressure of 14.7 psi.

As shown in by Table 3 and the figure above, the Example 1 tennis ballsmaintain rebound performance, exhibiting a rebound percentage decline ofless than 3% after four months of nonuse and exposure to atmosphericpressure upon removal from the sealed package/pressurized can. Incontrast, the WILSON® US OPEN tennis balls exhibit a loss ofapproximately 5.4% over two months, twice the loss in rebound ascompared to the Example 1 balls in half of the aging time.

The surprising and unexpected results indicate that Example 1 with asignificant thicker shell or core construction of at least 4.8 mm and aninternal pressure of less than 5 psi exhibit performance comparable to aconventional high performance pressurized tennis ball (the WILSON® USOPEN tennis ball). At the same time, the Example 1 tennis ball maintainsperformance significantly longer than the conventional tennis ball. As aresult, the Example 1 tennis ball may be played longer in terms of playas well as last longer for a player who plays recreationally as newballs would not necessarily be required each time that the recreationalplayer desires to play.

Moreover, because the Example 1 tennis balls have performance longevityin an atmospheric or non-pressurized environment, such balls may bestored and contained in sealed packages at a lower pressure or inunsealed packages with no pressure for significant periods of timewithout significant performance degradation. As a result, the Example 1tennis balls may be packaged in lower pressurized packages ornon-pressurized packages, reducing packaging cost and complexity.

Table 4 below provides various tennis ball characteristics andperformance data including internal ball pressure, weight, size,rebound, deformation, coefficient of restitution (COR) and permeationdata for: (1) a set of six PENN® CHAMPIONSHIP extra duty tennis ballsproduced by Head Technology GmbH of Austria; (2) a set of six DUNLOP®championship all court tennis balls produced by Dunlop InternationalEurope Ltd. of England; (3) a set of six WILSON® U.S. OPEN extra dutytennis balls; and (4) a set of six ZERO G PROTOTYPE tennis balls builtin accordance with an implementation of the present application. Theinternal ball pressure, size, weight, deformation, rebound height, andCOR values at different initial speeds taken of each of these tennisballs were measured when the balls were initially removed from theirrespective containers. The initial measurements were made within 1 hourof being initially removed unused from the tennis ball containers. Theball pressure, size, weight, deformation, rebound height and COR valueswere then re-measured after monthly time intervals. The tennis ballswere unused except for performing the above-listed measurements.

TABLE 4 COR PERMEATION TEST Time Cum. Out Ball Rbnd COR @ COR @ COR @ ofPress. Size Wght Def. Rbnd Loss 60 90 120 Can (psi) (in) (g) (in) (in)(in) fps fps fps Penn Init. 12.2 2.638 57.8 .224 57.9 .663 .559 .479Champ 1 mo. 9.1 2.630 57.2 .234 54.3 3.6 .628 .522 .438 Extra Duty 2 mo.7.5 2.618 57.5 .233 54.5 3.4 .620 .519 .440 Balls (Avg. 3 mo. 6.4 2.61257.3 .249 52.3 5.6 .606 .521 .430 of 6 balls) 4 mo. 5.0 2.613 57.7 .24551.6 6.3 .607 .506 .424 Dunlop Init. 9.5 2.600 58.4 .244 56.8 .637 .542.454 Champ All 1 mo. 7.4 2.592 58.1 .252 54.8 2.0 .626 .522 .444 CourtBalls 2 mo. 6.2 2.595 58.5 .265 53.6 3.2 .622 .507 .430 (Avg. of 6 3 mo.5.4 2.588 58.5 .272 52.3 4.5 .617 .501 .424 balls) 4 mo. 4.4 2.584 58.4.276 52.1 4.7 .608 .500 .418 Wilson US Init. 13.0 2.647 57.6 .231 57.5.651 .556 .480 Open Extra 2 mos. 8.8 2.623 56.9 .254 54.3 3.2 .640 .524.450 Duty Balls 4 mos. 6.5 2.617 56.9 .261 54.5 3.0 .613 .513 .440 (Avg.of 6 6 mos. 4.1 2.607 57.1 .275 52.4 5.1 .592 .484 .408 balls) Zero GInit. 4.9 2.697 58.6 .221 58.8 .649 .542 .454 Proto-type 2 mos. 1.82.695 57.9 .222 57.7 1.1 .641 .524 .439 Balls (Avg. 4 mos. 1.1 2.70058.0 .229 57.2 1.6 .621 .522 .434 of 6 balls) 6 mos. 0.7 2.695 57.9 .23156.8 2.0 .621 .522 .434

As shown by Table 4 above, the PENN® and DUNLOP® tennis balls under testalso experience substantial performance degradation upon removal fromtheir pressurized cans over prolonged periods of time. For example, therebound height of the PENN® CHAMPIONSHIP extra duty tennis balls droppedby over 6 percent after 1 month, approximately 10 percent after 3months, and over 10 percent after 4 months. Similarly, the DUNLOP®championship all court tennis balls exhibited a drop in rebound heightof over 3.5 percent after 1 month and approximately 8 percent after 3months. In contrast, the ZERO G PROTOTYPE tennis balls exhibit a reboundheight reduction of less than 1.9 percent after 2 months, less than 2.8percent after 4 months.

Accordingly, at least one of the tennis balls can be tested for reboundby vertically dropping the ball from a height of 100 inches off of agranite plate having a smooth surface and measuring the height of therebound of the bottom of the tennis ball from the smooth surface. Afirst tennis ball rebound height can be recorded by measuring therebound of the tennis ball within 1 hour of being initially removed fromthe tennis ball package and unused. A second tennis ball rebound heightcan be recorded by measuring the rebound of the tennis ball after thetennis ball is exposed to atmospheric pressure for four months andunused. In one implementation, the second rebound height is at least 96%of the first rebound height. In another implementation, the secondrebound height is at least 97% of the first rebound height.

Additionally, the tennis ball deformation of the PENN® CHAMPIONSHIPextra duty tennis balls and the DUNLOP® championship all court tennisballs also significantly degraded after being removed from theirpressurized containers and maintained in an environment of atmosphericpressure. The PENN® CHAMPIONSHIP extra duty tennis balls exhibited anincrease in tennis ball deformation after 1 month of over 4 percent, anincrease in tennis ball deformation after 2 months of over 4 percent,and increase in tennis ball deformation after 3 months of over 11percent. The DUNLOP® championship all court tennis balls exhibited anincrease in tennis ball deformation after 1 month of over 3 percent, anincrease in tennis ball deformation after 2 months of over 8.5 percent,an increase in tennis ball deformation after 3 months of over 11percent, and an increase in tennis ball deformation after 4 months ofover 13 percent. In contrast, the ZERO G PROTOTYPE tennis balls exhibitan increase in tennis ball deformation after 2 month of less than 0.5percent, and increase in tennis ball deformation after 4 months of less3.7 than percent.

Accordingly, when at least one of the tennis balls is tested fordeformation by applying a 3.5 lbf compressive pre-load to the ball andrecording a pre-load deformation value and then an additionalcompressive load of 18.0 lbf is applied and a second deformation valueis recorded, a tennis ball deformation can be calculated by subtractingthe pre-load deformation value from the second deformation value. Afirst tennis ball deformation can be recorded by measuring the tennisball deformation of the tennis ball within 1 hour of being initiallyremoved from the tennis ball package and unused. A second tennis balldeformation can be recorded by measuring the tennis ball deformation ofthe tennis ball after the tennis ball is exposed to atmospheric pressurefor four months and unused. In one implementation, the second tennisball deformation is no greater than 0.020 inches from the first tennisball deformation. In another implementation, the second tennis balldeformation is no greater than 0.015 inches from the first tennis balldeformation. The term “tennis ball deformation” shall mean a deformationvalue obtained by subtracting a pre-load tennis ball deformation valuefrom a second tennis ball deformation value, wherein the pre-load tennisball deformation value is measured after applying a 3.5 lbf compressivepre-load to a tennis ball and wherein the second tennis ball deformationvalue is measured after an additional compressive load of 18.0 lbf isapplied to the tennis ball.

Further, the reduction in the coefficient of restitution (“COR”) of thePENN® CHAMPIONSHIP extra duty tennis balls and the DUNLOP® championshipall court tennis balls is significantly greater after being removed fromtheir pressurized containers and maintained in an environment ofatmospheric pressure than the ZERO G PROTOTYPE tennis balls. Forexample, when tennis balls are projected at a predetermined velocity(e.g., 60 fps, 90 fps or 120 fps) against a vertically positioned,rigidly mounted steel plate having a smooth surface, the exit or returnvelocity of the tennis balls are measured using light gates. The ratioof the velocity of the tennis balls after impact (outbound) with thevelocity of the tennis balls before (inbound) impact is the COR. In oneimplementation, the velocity of the tennis balls is monitored usinglight gates, such as a model ADC VG03 produced by Automated DesignCorporation of Romeoville, Ill. As shown in Table 4, the COR wasmeasured at the predetermined speeds of 60 fps, 90 fps and 120 fps foreach of the balls initially within 1 hour of the balls being initiallyremoved from their respective packaging/containers unused. The CORvalues of the tennis balls were then retested at the predeterminedspeeds after the balls had been exposed to an atmospheric pressureenvironment for periods of 1 or more months.

At a predetermined inbound velocity of 90 fps, the PENN® CHAMPIONSHIPextra duty tennis balls exhibited a decrease in COR after 1 month ofover 6.5 percent, a decrease in COR after 2 months of over 7 percent, adecrease in COR after 3 months of approximately 7 percent, and adecrease in COR after 4 months of approximately 10 percent. The DUNLOP®championship all court tennis balls exhibited a decrease in COR after 1month of over 3.5 percent, a decrease in COR after 2 months of over 6percent, and a decrease in COR after 3 months of over 7 percent. Incontrast, the ZERO G PROTOTYPE tennis balls exhibit a decrease in CORafter 2 months of less than 3.5 percent, and a decrease in COR after 4months and 6 months of less than 4 percent. Accordingly, the ZERO GPROTOTYPE tennis balls exhibit a decrease in COR from an initial CORvalue of the unused tennis balls to a COR value taken 4 months after theunused tennis balls of 5 percent or less. In other words, a first CORvalue of at least one of the tennis balls can be taken within 1 hour ofbeing initially removed from the tennis ball package and unused from aninitial velocity of 90 feet/second, a second COR value of the tennisball after the tennis ball is exposed to atmospheric pressure for fourmonths can be recorded from an initial velocity of 90 feet/second, and,in one implementation, the second COR value is at least 95 percent ofthe first COR value.

Player testing was performed at various locations to determine theplayability characteristics between tennis balls formed in accordancewith an implementation of the present invention compared to the Wilson®US Open tennis balls, which are representative of a standard premiumpressurized tennis ball having an internal pressure of 13 psi. Testingwas performed with 103 players having NTRP (National Tennis RatingProgram) playing levels as shown in Table 5 below.

TABLE 5 Player Testing - Player Characterization: NTRP Rating # ofPlayers 5.0 or college player 56 4.5 25 4.0 11 3.5 or below 5 Unsure 6

Testing included both men and women college players from DePaulUniversity, Northern Illinois University and the University of SouthernCalifornia. Players were asked to play both the Wilson® US Open“control” tennis balls and the low pressure balls of Example 1, and thenrate the balls for the following attributes: sound, control, feel,consistency of bounce, speed and spin. The player testing results areillustrated in Table 6 below. The Example 1 tennis balls and the Wilson®US Open balls had the same appearance.

TABLE 6 Player Testing - Results: Preference Playability Wilson ®Characteristic Example 1 None US Open Sound 43.7% 9.7% 46.6% Control44.7% 9.7% 45.6% Feel 41.7% 11.7% 46.6% Bounce 35.9% 23.3% 40.8% Speed45.6% 12.6% 41.7% Spin 47.6% 16.5% 35.9% Overall 39.8% 12.6% 47.6%Preference

Results of player testing showed the following:

-   -   In all playability attributes, there was less than a 5%        difference in preference in all categories between the tennis        balls of Example 1 and the Wilson® US Open control tennis balls,        except for Spin. With respect to spin, the players preferred the        tennis balls of Example 1 over the US Open control tennis balls.    -   The player testing found that approximately 52% of the players        preferred the tennis balls of Example 1 or had no preference        between the two types of tennis balls.

Player testing illustrated that players felt there is a minimaldifference in all playability characteristics with the exception ofspin, and that the overall ball preference showed that, although theWilson® U.S. Open tennis balls were preferred by more players, 40% ofplayers preferred the tennis balls of Example 1 ball and 13% of playershad no preference between the two types of tennis balls. Our conclusionis that player testing shows that the Example 1 ball, which had lowerinitial ball pressure, exhibits comparable performance and is preferredby a significant percentage of players when compared to the U.S. Openpremium pressurized tennis balls.

FIG. 4 is a sectional view of an example tennis ball package 100. Thepackage 100 comprises a sealed package 102 and a set 104 of tennis balls10 (described above). Although package 100 is illustrated as comprisingthree of such tennis balls 10, in other implementations, package 100 maycomprise two tennis balls, four tennis balls, or greater than fourtennis balls 10.

The sealed package 102 can comprise a cylindrical can containing tennisballs 10. Sealed package 102 has an interior 106 containing tennis balls10 and sealed so as to have an internal pressure of no greater than 10psi. In one implementation, package 102 is sealed so as to have aninternal pressure of no greater than eight psi. In anotherimplementation, the package 102 is sealed so as to have an internalpressure of no greater than 5 psi. In other implementations, package 102is sealed so as to have an internal pressure less than that of theinternal pressure of the individual tennis balls 10. In oneimplementation, package 102 is sealed so as to have an internal pressureequal to atmospheric pressure, the pressure of the ambient environment.In such an implementation, the sealing of package 102 does not maintainthe internal pressure of package 102, but merely indicates that suchpackage 100 has not been tampered with or used, being in a “fresh”state.

In the example illustrated, package 102 comprises a cylindrical body 106having a floor 108 and cylindrical sidewalls 110. The top of body 106 isprovided with a top seal 112 and a removable cap or cover 114. The topseal 112 seals the interior 104. In one implementation, the top seal 112comprises a metallic panel, a portion of which may be scored tofacilitate peeling away of portions of the top seal to gain access tothe interior 104 and facilitate removal of balls 10. The removable cover114 resiliently snaps about or pops onto the top of body 106, over thetop seal 112. Top seal 112 assist in retaining balls 10 within interior104 during subsequent use, after top seal 112 has been broken orremoved.

As discussed above, the performance longevity of tennis balls 10 allowtennis balls 10 to be packaged in a lower pressure package. In someimplementations, the package containing tennis ball 10 may be atatmospheric pressure, eliminating the need to pressurize package 106during the packaging of tennis balls 10. The lower pressure package 102reduces the complexity and cost of packaging tennis balls 10. Inimplementations where package 102 is not pressurized, but is atatmospheric pressure, the top seal 112 may be omitted. In suchimplementations, tennis balls 10 may undergo post-manufacturingoperations at remote sites over space time intervals without such tennisballs having to be initially packaged in a pressurized package and thenrepackaged again in a pressurized package following such postmanufacturing operations. One example such post-manufacturing operationsis the application of logos to the exterior of such tennis balls.

Although package 102 is illustrated as a cylindrical can having ametallic ceiling panel and a removable top cap or cover, in otherimplementations, package 102 may have other configurations. In otherimplementations, the body 106 of the tennis ball package or containercan take other shapes, such as other cylindrical shapes, shapes havingpolygonal cross-sections, or other geometric shapes.

The ability of tennis balls 10 to have performance longevity at lowpressure conditions or at atmospheric pressure facilitates the use of awide range of packages. For example, in some implementations, package102 may comprise an air permeable package or an air permeable a net,wherein ceiling mechanisms simply indicate that the sold package has notbeen tampered with or previously opened, ensuring no prior use of thetennis balls at a point of sale.

Although the present disclosure has been described with reference toexample implementations, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the claimed subject matter. For example, although differentexample implementations may have been described as including featuresproviding one or more benefits, it is contemplated that the describedfeatures may be interchanged with one another or alternatively becombined with one another in the described example implementations or inother alternative implementations. Because the technology of the presentdisclosure is relatively complex, not all changes in the technology areforeseeable. The present disclosure described with reference to theexample implementations and set forth in the following claims ismanifestly intended to be as broad as possible. For example, unlessspecifically otherwise noted, the claims reciting a single particularelement also encompass a plurality of such particular elements. Theterms “first”, “second”, “third” and so on in the claims merelydistinguish different elements and, unless otherwise stated, are not tobe specifically associated with a particular order or particularnumbering of elements in the disclosure.

1. A tennis ball comprising: a spherical hollow elastomeric core havinga specific gravity of less than 1 and a thickness of at least 4.5 mm;and a textile layer covering the spherical hollow core.
 2. The tennisball of claim 1, wherein the spherical hollow core has an internalpressure of no greater than 5 psi.
 3. The tennis ball of claim 1,wherein the spherical core comprises one or more thermoplastic ethylenecopolymers, each having a specific gravity of less than or equal to 0.9.4. The tennis ball of claim 3, wherein the thermoplastic ethylenecopolymer has a flexural modulus of less than 35 MPA and a shore Dhardness of less than
 30. 5. The tennis ball of claim 4, wherein thethermoplastic ethylene copolymer has a flexural modulus of less than orequal to 25 MPA.
 6. The tennis ball of claim 3, wherein thethermoplastic ethylene copolymer is comprised of ethylene and an alkene.7. The tennis ball of claim 3, wherein the ethylene copolymer includesan alkene selected from the group consisting of butane, hexene, octene,pentene, heptene, nonene and decene.
 8. The tennis ball of claim 1,wherein core has a thickness of no greater than 5.1 mm.
 9. The tennisball of claim 1, wherein the core comprises: at least one rubberselected from a group of rubbers consisting of: natural rubber,polybutadiene, isoprene, styrene-butadiene rubber and mixtures thereof;and a thermoplastic ethylene copolymer in an amount of within the rangeof 10 to 100 parts per hundred with a specific gravity of less than orequal to 0.9.
 10. The tennis ball of claim 1, wherein the textile layercomprises a woven fiber material.
 11. The tennis ball of claim 1,wherein the textile layer comprises a needle-punched fiber material. 12.The tennis ball of claim 1, wherein the tennis ball is a competitiveplay tennis ball having characteristics that satisfy United StatesTennis Association and International Tennis Federation standardizedspecifications as published by the International Tennis Federation as ofJul. 1,
 2018. 13. The tennis ball of claim 1, wherein the tennis ballhas a moment of inertia of less than 1.85 oz in^(t).
 14. The tennis ballof claim 1, wherein the tennis ball has a moment of inertia of less than1.80 oz in^(t).
 15. The tennis ball of claim 1, wherein the core has athickness of at least 4.8 mm.
 16. A tennis ball package comprising: apackage having an internal pressure of no greater than 10 psi; aplurality of tennis balls within the package, at least one of theplurality of tennis balls having, a first tennis ball coefficient ofrestitution value of at least 0.53 when measured from an initialvelocity of 90 feet/second within 1 hour of the at least one of theplurality of tennis balls being initially removed from the tennis ballpackage and unused, and a second tennis ball coefficient of restitutionvalue measured from an initial velocity of 90 feet/second after the atleast one of the plurality of tennis balls is exposed to atmosphericpressure for four months, and wherein the second coefficient ofrestitution value is at least 95 percent of the first coefficient ofrestitution value, wherein each of the plurality of tennis ballscomprises: a spherical hollow elastomeric core having a specific gravityof less than 1 and a thickness of at least 4.5 mm; and a textile layercovering the spherical hollow core.
 17. The tennis ball package of claim16, wherein the second coefficient of restitution value is at least 96percent of the first coefficient of restitution value.
 18. The tennisball package of claim 16, wherein at least one of plurality of tennisballs has a first tennis ball rebound height recorded within one hour ofthe at least one of the plurality of tennis balls being initiallyremoved from the tennis ball package, wherein the at least one ofplurality of tennis balls has a second tennis ball rebound heightrecorded after the at least one of the plurality of tennis balls isexposed to atmospheric pressure for four months and unused, and whereinthe second tennis ball rebound height at least 96% of the first tennisball rebound height.
 19. The tennis ball package of claim 18, whereinthe second tennis ball rebound height at least 97% of the first tennisball rebound height.
 20. The tennis ball package of claim 16, whereinthe package has an internal pressure of no greater than 5 psi
 21. Thetennis ball package of claim 16, wherein at least one of the pluralityof tennis balls has a first tennis ball deformation measured within 1hour of the at least one of the plurality of tennis balls beinginitially removed from the tennis ball package and unused, wherein theat least one of the plurality of tennis balls has a second tennis balldeformation recorded after the at least one of the plurality of tennisballs is exposed to atmospheric pressure for four months and unused, andwherein the second tennis ball deformation is no greater than 0.020inches from the first tennis ball deformation.
 22. The tennis ball ofclaim 21, wherein the second tennis ball deformation is no greater than0.015 inches from the first tennis ball deformation.
 23. The tennis ballpackage of claim 16, wherein each of the plurality of tennis ballscomprises: a spherical hollow elastomeric core having a specific gravityof less than 1 and a thickness of at least 4.5 mm; and a textile layercovering the spherical hollow core.
 24. The tennis ball package of claim23, wherein the spherical hollow core has an internal pressure of nogreater than 5 psi.
 25. The tennis ball package of claim 23, wherein thespherical core comprises an ethylene copolymer having a specific gravityof less than 0.9.
 26. The tennis ball package of claim 26, wherein theethylene copolymer has a flexural modulus of less than 25 MPA and ashore D hardness of less than
 30. 27. The tennis ball package of claim23, wherein core has a thickness of no greater than 5.1 mm.
 28. Thetennis ball package of claim 16, wherein each of the plurality of tennisballs is a competitive play tennis ball having characteristics thatsatisfy United States Tennis Association and International TennisFederation standardized specifications as published by the InternationalTennis Federation as of Jul. 1,
 2018. 29. The tennis ball of claim 1,wherein the spherical core comprises a thermoplastic material having aspecific gravity of less than or equal to 0.9.